Re: [PATCH v4 21/42] virtio_net: get rid of virtio_net_hdr/skb_vnet_hdr

From: Michael S. Tsirkin
Date: Wed Nov 26 2014 - 08:12:25 EST


On Wed, Nov 26, 2014 at 01:50:53PM +0100, Cornelia Huck wrote:
> On Tue, 25 Nov 2014 18:42:53 +0200
> "Michael S. Tsirkin" <mst@xxxxxxxxxx> wrote:
>
> > virtio 1.0 doesn't use virtio_net_hdr anymore, and in fact, it's not
> > really useful since virtio_net_hdr_mrg_rxbuf includes that as the first
> > field anyway.
> >
> > Let's drop it, precalculate header len and store within vi instead.
> >
> > This way we can also remove struct skb_vnet_hdr.
> >
> > Signed-off-by: Michael S. Tsirkin <mst@xxxxxxxxxx>
> > ---
> > drivers/net/virtio_net.c | 90 ++++++++++++++++++++++--------------------------
> > 1 file changed, 41 insertions(+), 49 deletions(-)
> >
>
> > @@ -260,13 +256,11 @@ static struct sk_buff *page_to_skb(struct virtnet_info *vi,
> >
> > hdr = skb_vnet_hdr(skb);
> >
> > - if (vi->mergeable_rx_bufs) {
> > - hdr_len = sizeof hdr->mhdr;
> > - hdr_padded_len = sizeof hdr->mhdr;
> > - } else {
> > - hdr_len = sizeof hdr->hdr;
> > + hdr_len = vi->hdr_len;
> > + if (vi->mergeable_rx_bufs)
> > + hdr_padded_len = sizeof *hdr;
>
> sizeof without () looks weird to me.

It's how it was originally, so I think I'd rather keep it.
I kind of like it too: it stresses the fact that sizeof is not a function
and so does not actually dereference the pointer
even though it looks like it does.

We can change it with a patch on top, but should then be changed
everywhere in this file.

> > + else
> > hdr_padded_len = sizeof(struct padded_vnet_hdr);
> > - }
> >
> > memcpy(hdr, p, hdr_len);
> >
>
> Otherwise:
>
> Reviewed-by: Cornelia Huck <cornelia.huck@xxxxxxxxxx>
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